Manufacture of titanium dioxide pigments



- metal is capable of forming an oxide under the Patented Dec. 8, 1942 MANUFACTURE OF TITANIUM DIOXIDE. PIGMENTS Isaac Ephraim Weber and Arthur Neville Copna Bennett, Luton, England No Drawing. Application May 13, 1940, serial No. 335,014. In Great Britain May 18, 1939 13 Claims. (01. 106-292) Titanium dioxide, alone or in the form of a of an ionising gas; this treatment is known composite pigment, is used in the manufacture of as. elektrionisation and/or voltolisation and paints, lacquers, enamels, plastics artificial silk products of the treatment are known under the and in the compounding of rubber and in many names Elektrion and Voltol. other ways. It is necessary for the titanium Where producer gas is used as theheating dioxide to have certain desirable properties which agent and where it may not be possible to mix the are associated with fastness to light, resistance metal or metallic compound with the.heating to weathering, oil absorption and wetting out agent the metal or metallic compound may be properties both in water and oil media. volatilised in such a way that it passes with the This invention is concerned with the improveheating agent into the furnace. There are many ment of these properties. It is customary to ways in which this can bedone; for instance, the start with titanium dioxide from the hydrolysis metal or compound of the metal is allowed to of an acid titanium saltsolution, to wash it and pass into the combustion chamber between the to calcine it in order to give it pigmentary propproducer and the furnace containing the titaerties. I nium dioxide. The heated metal or its com- The titanium dioxide may be calcined in any pound may be volatilised outside the main source of the well known ways. The titanium dioxide of heat which is being used in the calcination of may be calcined either continuously or in batch the titanium dioxide and carried into the comeither in a stationary furnace or in a rotary bustion chamber by means of air or steam. The furnace. The heating may be by oil, producer volatilised or non-volatilised metal or compound gas or by any other means, direct or indirect. of metalmay be introduced at various parts of This invention consists in improving the aforethe furnace should this be desirable. Thus in a said properties of the titanium dioxide by subcontinuous rotary furnace the titanium dioxide jecting the titanium dioxide during the heating will have-passed through different stages of to the vapour of a metal or metal compound, temperature between its entering and leaving this vapour either being introduced into the furthe fumaceand thevolatilised metal or its comnace as such orbeing formed formed therein pound can be introducedat any particular stage from a suitable metal or metalcompound introin order to give variation in the properties of duced into the furnace otherwise than in admixthe titanium dioxide pigment.

ture with the titanium dioxide. v The invention afiords a readily controlled In carrying out the invention, the vapour of method of treating titanium dioxide during cala metal or metal compound may be produced by cination with varying quantities of metal. volatilisation at the entrance tothe furnace. Metals and their compounds which may be For example, where fuel oil is used as a heating used for improving'the properties of the titaagent for calcining the titanium dioxide the as nium dioxide ar f xa p n m y, zinc. metal in a finely divided state is 'mixed with lead, cadmium, aluminium, although we do not the oil and the mixture is passed together through limit ourselves. to these particular metals. the oil burner into the furnace. Where the finely Although reference has been made to tita-.

divided metal is not readily miscible with the oil nium dioxide, we mean. by this titanium dioxideit may be kept in suspension by the addition of 40 whether alone or admixed withother compounds 5 Small ty of a suspending agent. The which are capable of giving composite pigments.

metal is volatilised in the flame from the burner The following examples illustrate the invenso that the pigment is heated in the presence l of the volatilised metal or its oxide, where the Examplel conditions which obtain in the furnace. 7 b of zinc oxide were mixed to form a very Instead of the metal one may incorporate thick paste with 1 lbs. of ionised oil and the with the OH a compound of the metal miscible Paste was then thoro h y mixed with 9 gallons with the oil or dispersible therein and generally of fuel oil. The zinc oxide was so dispersed that speaking an organic compound of the metal will P a y not w s deposited from the 8118- ,be suitable oran oxide of the metal. Uniform pension durin a period Of Several hOuYS- The admixture of the metal compound with the oil 'fuel'oil containing the zinc oxide was used for may be assisted by the addition of an ionised firing a rotaryfurnace in which titanium dioxoil, that is, an oil which has been subjected to ide was calcined by the continuous method at a a high tension electric discharge in the presence temperature of approximately 900 (2; The oil was fed to the burners of the furnace at the rate of 9.5 gallons per hour and the furnace wasoperated so that titanium dioxide was discharged at the rate of 224 lbs. of the dry dioxide per hour. The pigment produced in this manner had the following properties:

Whereas a titanium dioxide produced without treatment with zinc fume showed a tendency to chalk after a short time, a pigment produced according to the example only chalked slightly after a period ten times as long. The pigment had better wetting out properties than one produced in like manner without thetreatment with ,zinc fume.

The oil absorption of the pigment produced by the method of the example is only two-thirds that of a pigment produced without the zinc fume treatment.

The oil absorption of the pigments may be determined as follows: 3 grams of the pigment are placed on a glass tile and carefully mixed by means of a spatula with refined linseed oil added drop by drop from a graduated burette. Addition of the oil is continued until an end point is reached at which no change of contour is ob- .the fuel oil and remained in suspension sufficiently long to enable the mixture to be fed through a burner to a continuously operated calcination furnace. The fuel oil containing the antimony oxide was fed to the furnace at the rate of 10 gallons per hour whilst the titanium dioxide left the furnace at the rate of 224 lbs. of dry titanium dioxide per hour. The temperature in the furnace was approximately 900 C. The titanium pigment so obtained had improved weathering properties and fastness to light.

Example 3 17 lbs. of zinc naphthenate were dissolved in 1o gallons of warm fuel oil, in which it dissolves veryrapidly to give a solution homogeneous in appearance. The fuel oil containing the zinc naphthenate wasfed to the furnace at the rate of 10 gallons per hour whilst the titanium dioxide left the furnace at the rate of 224 lbs. of dry titanium dioxide per hour. The temperature in the furnace was approximately 900 C. The pig-.

mentso obtained was improved in respect of its chalking and wetting out properties in compariwithout use of zinc naphthen Example 4 Titanium dioxide pulp containing approxison with a pigment prepared in like manner mately 37 per cent. of solids is fed into a rotary furnace fired by producer gas in which it is calcined at a temperature of approximately 900 0. Titanium dioxide leaves the furnace at the rate of 224 lbs. per hour. Cadmium metal is fed into the combustion chamber of the furnace-either in Y the form of rod or powder at the rate of 9 lbs.

'per hour. The cadmiumreadily. volatilis e's and passes into the rotary furnace- The presence of cadmium vapour in the furnace results .in an improvement in theweathering, oil absorption and wetting out properties of the pigment.

1. A process for the production of improved titanium dioxide pigments, wherein titanium dioxide is calcined in an atmosphere containing the vapor of a substance selected from the group consisting of metals and compounds of metals,

the said vapor being generated from a substance of the said group which is out of contact with the titanium dioxide.

2. A process as claimed in claim 1, wherein the calcination is conducted'in a furnace fired by liquid fuel in which is suspended a finely di compounds of metals, the vapor being carried v into the furnace with the heating gases.

4. A process as claimed in claim '1, wherein the calcination is conducted in a furnace fired by gaseous fuel and the vapour of a substance belonging to the group consisting of metals and compounds of metals is introduced into the combustion chamber of the furnace and is carried into the furnace with the heating gases.

5. A process for the production of improved titanium dioxide pigments, wherein titanium dioxide is calcined in an atmosphere containing the vapour of a substance selected from the group consisting of antimony, zinc, lead, cadmium and their compounds, the said vapour being generated from a substance of the said group which is out of contact with the titanium dioxide.

6. A process as claimed in claim 5, wherein.

the calcination is conducted in a furnace fired by liquid fuel in which is. suspended a finely divided material which forms vapour of a subf stance selected from the group consisting of antimony, zinc, lead, cadmium and their compounds in the flame resulting from the combustion of the fuel.

7. A process as claimed in claim 5, wherein the calcination is conducted in a furnaceefired by gaseous fuel and there is introduced into the combustion chamber of the furnace a material which forms therein vapour of a substance selected from the group consisting of antimony, zinc, lead, cadmium and their compounds, the vapour being carried into the furnace with the heating gases.

8..A process as claimed in claim 5, wherein the calcination is conducted in a furnace fired by gaseous fuel and the vapour of a substance selected from the group consisting of antimony, zinc, lead, cadmium, and their compounds is introduced into the combustion chamber of the furnace and is carried into the furnace with the heating gases.

9. A process for the production offiimproved" I titanium dioxide pigments comprising the step of calcining titanium dioxide,'wherein the vapour of a substance belonging to the group consisting of metals and compounds of metals is.

sisting of antimony, zinc, lead, cadmium and their compounds is introduced into the calcining furnace during the calcination.

11. A process for theproduction of improved.

' wherein titanium dioxide is calcined in a furnace fired by liquid fuel in which is suspended anti- 15 mony oxide, the vapor of a substance belonging to the groupfconsisting of antimony and com pounds of antimony being thereby formed in the flame resulting from the combustion of the fuel.

13. A process for the production of improved titanium dioxide pigments as claimed in-claim 5,

wherein titanium dioxide is calcined in a furnace fired by liquid fuel in which is suspended zinc naphthenate, the vapor of a substance belonging to the group consisting of,zinc and compounds of zinc being thereby formed in the flame resulting from the combustion of the fuel.

ISAAC EPHRAIM WEBER. p ARTHUR NEVILLE COPNALL BENNETT. 

